Zoom lenses in which negative, positive and positive lens groups are arranged in this order from an object side have been known (see, for instance, Japanese Laid-open Patent Applications H4-114116 and H10-39214).
Generally, arranging a negative lens group nearest the object side is advantageous in widening the viewing angle and, also, the back focus is easily kept sufficient using such an arrangement. On the other hand, this causes the lens system as a whole to have an asymmetrical configuration so that the fluctuation of aberrations due to zooming becomes large and it becomes difficult to obtain sufficient optical performance over the entire range of zooming.
In the above-mentioned Japanese Laid-open Patent Application H4-114116, it is described that a negative first lens group consists of a cemented negative lens element and a positive lens element. The number of lens elements is small and miniaturization is achieved. However, wide picture angles that are considered advantageous in this lens type are not provided.
Moreover, in the above-mentioned Japanese Laid-open Patent Application H10-39214, it is described that a negative first lens group consists of two negative lens elements and one positive lens element. In this configuration, the first lens group has the advantage of correcting aberrations. On the other hand, the first lens group has a relatively large outer lens diameter and consists of three lens elements. This is disadvantageous concerning miniaturization. Accordingly, it is difficult to simultaneously satisfy the desire for wider viewing angles and miniaturization.
The present invention relates to a wide-angle zoom lens and, more particularly, it relates to a wide-angle zoom lens for use in a video camera, an electronic still camera, etc., in which a CCD is installed. The object of the present invention is to provide a wide-angle zoom lens that satisfies both the need for wider picture angles and miniaturization while exhibiting a high optical performance over the entire range of zoom.